There is known a sheet member feed apparatus having a pair of feed rollers for use in a copying machine such as an electrophotographic machine and the like.
FIG. 6 schematically illustrates the bearing arrangement for one side of such known sheet member feed apparatus.
Referring to FIG. 6, an elongated bearing installation hole (hereinafter referred to as "elongated hole") 3 is provided in a side plate of a frame (not shown) for an upper feed roller 1. A bearing 6 is installed to be movable upwardly and downwardly in the elongated hole 3, with a clearance d remaining between bearing 6 and the surrounding inner wall faces defining the elongated hole 3.
Axis 5 of the upper feed roller 1 is fixed to the bearing 6. Biasing spring 4 is extended over a projected portion of the bearing 6 so as to urge the upper roller 1 downwardly against a lower roller 2.
In this known sheet member feed apparatus, since the biasing spring 4 is simply placed around the bearing 6 in the manner explained above and since a clearance remains between the bearing 6 and the surrounding inner wall faces 3a of the elongated hole 3, a force f1 to urge the upper roller 1 against the lower roller 2 is effected only from the center of the axis 5 of the upper roller 1 toward the center of an axis 8 fixed to a bearing 10 of the lower roller 2 and is directed downward in a direction such that the bearing 6 moves toward the bottom inner face of the elongated hole 3.
As long as the movement of the bearing 6 remains in a vertical direction, chattering is not generated since sufficient clearance exists to allow smooth movement of the bearing 6 in the elongated hole 3, and the movement of the bearing 6 is restricted appropriately by the action of the biasing spring 4 and also the action of the lower roller 2.
However, in such known sheet member feed apparatus, it actually often occurs that the bearing 6 rolls from side to side during the operation of the apparatus, such that impacts occur between outer side faces 6a of the bearing 6 and inner wall side faces 3a of the elongated hole 3, thereby unavoidably generating chattering causing not only mechanical defects but also other disadvantages, for instance, such as:
(i) unpleasant noise is generated, PA1 (ii) mechanical friction is caused, thus decreasing durability of the apparatus, and PA1 (iii) in the case of an electrophotographic copying machine, undesired pressure is imparted to a copied paper, thus causing damage to images developed thereon and the like.
The occurrence of such chattering is due to the fact that the rotational force in the rolling operation of the upper roller 1 and the lower roller 2 is affected to the bearing 6 in the same direction so that of the rotation of the roller 1. Thus, one end portion of one outer side wall 6a and the opposite end portion of the other outer side wall 6a of the bearing 6 individually impact against the corresponding inner side wall faces 3a of the elongated hole 3, since the tolerance of the elongated hole 3 enabling movement of the bearing 6 is limited. Since the biasing spring 4 is urged or charged in the rotational direction of the bearing 6, a reaction force of the biasing spring 4 acts on the bearing 6 to impart a rotational force of the biasing spring 4 to the bearing 6 in the direction opposite to the direction of rotation of the upper roller 1. As a result, the outer wall face ends of the bearing 6 repeatedly impact against inner wall side faces of the elongated hole 3, whereby the rotation of the bearing 6 is restricted.